Participation of transplanted cells in chimeras by 24 hr. Eggs that were to serve as donors were microinjected with fluorescein dextran. After incubation at 27°C overnight the chimeric embryos were examined and photographed separately under the Nomarski channel and fluorescein channel of a confocal microscope (Bio-Rad). The two images were merged and the fluorescent donor cells were shown as green-yellow pseudocolor. Length of the full embryo is about 1.6 mm.

Pigmentation in a 3-day-old chimera. After incubation at 26-27°C for 3 days, wild-type (a), albino (b), and chimeric (c) embryos were examined and photographed with a Nikon microscope. Size of the fish head is about 500 μm.

Pigmentation in adult chimeras. Adult albino (a), wild type (b), or chimeras (c-j) were anesthetized as described (14) and photographed using a Contax MT50 camera mounted with a 1:1 macro lens. Note that for the chimeras in c and d both sides of each fish are shown, for chimeras in e-j only one side. Fish size is about 1 inch.

Progeny of a germ-line chimera. Chimera 5-5-3 (Fig. 4i) was pair-mated with an albino female and their offspring were incubated at 27°C for 30 hr and photographed under a dissecting microscope. Diameter of the embryo is about 600 μm.

Southern analysis of DNA from pigmented and albino offspring of chimera 5-5-3 showing inheritance of the transgene in some pigmented offspring. Pst I digests of genomic DNA from individual fish were analyzed as described under Materials and Methods. Lane 1, albino fish DNA to which was added 50 pg of the RSV-lacZ plasmid, equivalent to approximately two copies per diploid genome; lane 2, albino fish DNA; lane 3, DNA from a heterozygous M9-1 donor transgenic fish; lanes 4-8, DNA from five individual pigmented offspring of chimera 5-5-3, three of which inherited the lacZ gene; lanes 9-11, DNA from three individual albino offspring of chimera 5-5-3, none ofthem carried the lacZ gene. kb, Kilobase(s).